(* Expresiones aritmeticas *)
Inductive ArithExp : Set := 
  | arith_exp_num   : Integer  -> ArithExp
  | arith_exp_id    : Id       -> ArithExp
  | arith_exp_plus  : ArithExp -> ArithExp -> ArithExp
  | arith_exp_minus : ArithExp -> ArithExp -> ArithExp
  | arith_exp_mult  : ArithExp -> ArithExp -> ArithExp
  | arith_exp_div   : ArithExp -> ArithExp -> ArithExp
  | arith_exp_mod   : ArithExp -> ArithExp -> ArithExp
.